Mounting rails for securing passenger seats in commercial aircraft are normally standardized. One such standard defining sheets is, for example, air traffic standard LN 29 890. The standard construction of such rails includes a lower mounting rail section having an Ω- or a T-cross-sectional configuration. A chair securing upper rail section includes a C-cross-sectional configuration that opens upwardly into the cabin, whereby the upwardly facing opening is bounded on both sides by two flanges that reach toward and face each other to form a slot. The slot has spaced bores for the insertion of a seat footing. The seat securing upper section with the C-cross-sectional configuration and the rail mounting lower section are conventionally made of the same metal and are provided for example as extruded or milled stock.
Such chair mounting rails for the releasable securing of seats and other items in the C-portion of the upper rail section have standardized dimensions. German Patent Publication DE 42 24 821 A1 describes such a seat mounting rail. Further, Russian Patent RU 2,136,548 C1 discloses a device for the securing of passenger seats in which the mounting rail comprises edge shaped elements for the securing of the passenger seats in the mounting rail. U.S. Patent Publication U.S. Pat. No. 6,554,225 B1 discloses an arrangement of mounting rails in a lightweight floor construction for an aircraft. The floor is constructed for mounting rails having a T-cross-sectional configuration in the floor structure of an aircraft.
Mounting rails used in the known constructions are generally made of a high strength aluminum alloy with due regard to weight considerations. High strength aluminum alloys of the aluminum-zinc-group are particularly suitable for manufacturing conventional seat mounting rails. These aluminum zinc alloys are also referred to as so-called 7XXX alloys which have a high mechanical strength. Thus, these alloys have been recognized as particularly suitable for manufacturing seat mounting rails which are exposed to high mechanical loads in an aircraft structure.
However, it has been found that satisfying mechanical characteristics alone is not entirely satisfactory since other characteristics are also required. For example, a resistance against corrosion is important for seat mounting rails in an aircraft since the floor in the aircraft cabin is exposed to a multitude of corrosive influences or loads such as spilled liquids, condensed moisture, and the like. A possible measure for preventing corrosion of the seat mounting rails is the use of additional rail coverings as is disclosed in U.S. Pat. No. 6,498,297 B2 and U.S. Pat. No. 4,475,701. Another possibility of protecting seat mounting rails against corrosion is to increase the corrosion resistance of the rail material itself. This approach requires using corrosion resistant materials for manufacturing the rails. Thus it is known to make the entire seat mounting rail of high strength titanium alloys, particularly as defined in the alloy material Ti-6Al-4V.
The use of titanium alloys for manufacturing seat mounting rails clearly has the advantage of a material highly resistant to corrosion. However, titanium alloys are substantially more expensive than aluminum alloys and additionally have a higher density than aluminum alloys which is not advantageous with regard to the constant need for weight reductions in the manufacture of commercial aircraft. More specifically, a seat mounting rail of a titanium alloy is about 30% heavier than a comparable seat mounting rail made of a high strength aluminum alloy. As a result, seat rails made of high strength titanium alloys increase the overall floor weight of a commercial aircraft by several hundred kilograms. At the same time, the use of seat mounting rails made of titanium alloys makes the floor structure substantially more expensive so that the described solution of the corrosion problem is economically not acceptable. More specifically, solving the corrosion problem by a titanium seat mounting rail which is about ten times more expensive than a comparable conventional aluminum alloy rail is not acceptable.